A liquid crystal display device is incorporated in various devices including a television receiver, vehicle-mounted display such as car navigation equipment and the like, notebook-size personal computer, tablet PC, cellular telephone, and mobile terminal such as a smartphone, and the like.
An active-matrix liquid crystal display device is provided with an active area including pixels arranged in a matrix form. An active area is provided with gate lines extending along rows in which pixels are arranged, source lines extending along columns, and switching elements arranged in the vicinities of positions at which the source lines and the gate lines cross each other. Further, as a switching element of an active-matrix liquid crystal display device, a thin-film transistor (TFT) utilizing low-temperature polysilicon (LTPS) is widely used.
Incidentally, in a TFT utilizing LTPS, there is a problem that a pixel voltage is changed by a light leak thereby causing a flicker. For this reason, a liquid crystal display device provided with a TFT utilizing LTPS is configured to shade, for example, backlight by being provided with a light-shielding layer.
In recent years, in a liquid crystal display device, the trend toward higher definition and higher aperture is further enhanced, and hence the retention capacity of the individual pixel is gradually becoming smaller. Along with such a trend, the parasitic capacitance tends to increase owing to the proximity of the light-shielding layer and the source line to each other. As a result, there is a problem that the potential of the shielding-layer provided in an electrically-floating state is changed by the potential of the source line, whereby the characteristics of the TFT are changed and the display quality is lowered.
On the other hand, a liquid crystal display device with an in-cell type touch detection function in which a common electrode for display originally provided in the liquid crystal display device is used also as an electrode for a touch sensor is proposed. In this liquid crystal display device too, it is required that the lowering of the sensitivity of the touch sensor resulting from a change in the potential of the light-shielding layer be prevented from occurring.